Selection of Lactic Acid Bacteria from Dairy Matrices with Antifungal Activity to be Used as Biopreservative Adjunct Cultures

This research aims to select the potential lactic acid bacteria (LAB) for starter culture for cocoa beans fermentation. The bio-control activity against mycotoxigenic fungi were also evaluated. The indigenous LAB was analized from Sukabumi cocoa beans fermentation by spontaneous method for four days (96 hours). The preliminary screening of LAB were observed by clear zone forming, morphology characterization and catalase activity. The LAB were screened for their ability to resist acidity, ethanol, and heat, and their ability to produce high acid and antifungal. The antifungal capability was antagonistic assays to Aspergillus ochraceus IPBCC 88.033 on Potato Dextrose Agar (PDA) medium. The result showed that the selected acid bacteria isolate, H 2.34, were antifungal-producing strains, and resist acidity, ethanol and heat, which was suitable property for starter culture and biopreservation agent. The study demonstrated the selection of local Indonesian LAB from Sukabumi fermented cocoa bean to observe the potential of isolate as a starter culture and biopreservation agent

The diversity of lactic acid bacteria (LAB) species in donkey's milk was analysed by culture-dependent microbial techniques. Dominant strains were isolated on agar media generally used for enumerating LAB. To enrich the number of acidifying LAB present, the milk samples were incubated at 37°C for 24h (cultured milk samples, CM). One of the CM samples was heat-treated at 63°C for 10min before incubation at 37°C (heat-treated and cultured milk sample, TCM) to select thermophilic LAB. The microflora in these CM and TCM samples was then compared to that of the raw milk samples (RM). Among the 129 LAB isolates, 10 different species (four Enterococcus, five Streptococcus and one Pediococcus) were identified by molecular methods. Although the 10 LAB species were present in the RM samples, only three and two isolates were found in CM and TCM samples, respectively. Despite the selection protocol being set up to favour the isolation of all LAB isolates present in donkey milk, relatively few species and biotypes were isolated. No LAB isolates belonging to the most technologically important dairy starter species were detected. The possible factors related to the limited LAB diversity in donkey's milk have been discussed below. There is increased interest in using donkey's milk as a source of human nutrition. The large amounts of antimicrobial components and defence factors present in donkey's milk provide protection from microbial infections and distinguish donkey's milk from the milks of other mammals. However, the microbiota in donkey's milk has so far been poorly characterized, specifically with regard to the lactic acid bacteria (LAB). This study has identified cultivable, acidifying and thermoduric LAB that could be used to develop starter cultures. This is the first study to investigate the culturable LAB microbiota present in donkey's milk.

Wheat flour is one of the most common causative agents of food allergy. The study presents the selection and characterization of lactic acid bacteria (LAB) strains capable of hydrolyzing/modifying allergenic proteins of wheat flour. Hydrolysis of wheat proteins was determined with sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting with sera from patients with food allergy to gluten. The analysis of electrophoretic profiles of protein extracted from sourdough shows the capability of selected LAB strains for proteolytic degradation of wheat proteins that belong to two factions: albumin/globulin (hydrolysis of 13 polypeptides with a molecular weight between 103 and 22 kDa); and gliadin (seven polypeptides with a molecular weight between 39 and 24 kDa). All analyzed strains were capable of hydrolyzing some IgE-binding epitopes of wheat allergens. The lack of such changes in control samples indicates that they were induced rather by the proteolytic activity of bacterial strains than endogenous enzymes of wheat flour. The gluten proteins were susceptible to hydrolysis by sequential digestion with pepsin and trypsin. The selected strains exhibit proteolytic activity, which leads to a reduction in allergenicity of wheat sourdoughs. These strains may be applied as specific starter cultures to prepare bakery products of special nutritional use. © 2015 Society of Chemical Industry.

Evaluation of a bacteriocin-producing strain of Pediococcus acidilactici as a biopreservative for “Alheira”, a fermented meat sausage

Selection of lactic acid bacteria as biopreservation agents and optimization of their mode of application for the control of Listeria monocytogenes in ready-to-eat cooked meat products

The aim of this study was to investigate the effects of autochthonous Lactobacillus plantarum strains (S50, S51, S72, S74, and S85) as starter cultures on growth of Listeria monocytogenes in sucuk (Turkish dry fermented sausage) production. The counts of L. monocytogenes, lactic acid bacteria, and Enterobacteriaceae as well as pH value and moisture content were determined in sucuk during ripening period. L. monocytogenes, lactic acid bacteria, and pH value were significantly affected (p < 0.01) by both starter culture and ripening period. A slight increase in L. monocytogenes count was observed in the control group whereas a reduction was observed in samples produced with L. plantarum strains at the first day of fermentation. Although L. monocytogenes reduction in control group with spontaneous microbiota was 0.54 log cfu/g after 11 days of ripening, reductions of as high as 2.74 log cfu/g was observed in the presence of L. plantarum S50.Practical applicationsIn the current study, five different autochthonous Lactobacillus plantarum isolates were identified, the effects of these strains on the behavior of Listeria monocytogenes in Turkish fermented sausage (sucuk) were determined. To the best of our knowledge, this is the first report investigating the effects of autochthonous lactic acid bacteria strains on behavior of L. monocytogenes in sucuk fermentation. As starter culture autochthonous lactic acid bacteria can be more competitive than commercial types. Our findings reveal the importance of the use of these autochthonous L. plantarum strains causes rapid pH drop to inhibit L. monocytogenes growth during sucuk fermentation. And also L. plantarum S50 strain may be more suitable for use as bioprotective culture or starter culture compared to other strains.

Selection of lactic acid bacteria from home-made sourdoughs for resistance to the main almond skin polyphenols

Copyright: © 2012 Ntougias S. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Lactic acid fermentation is an important process used in the production of several food and beverages. Optimization of lactic acid fermentation improves product quality by positively affecting preservation, organoleptic characteristics and nutritional value [1]. Numerous attempts were made to identify novel lactic acid bacteria as starters in order to achieve effective monitoring of the fermentation process. Starter cultures of lactic acid bacteria can provide long-term safe storage, contributing highly to the improvement of flavor and the development of pleasant organoleptic characteristics [2]. Lactic acid bacteria act protectively against food-borne pathogens, exhibiting probiotic properties [3,4]. Several criteria have been proposed for the selection of lactic acid bacteria as starters, e.g. fermentation type (homo and hetero-fermentation), halotolerance and bacteriocin production [2]. Besides, attention was drawn to the role of nonstarter lactic acid bacteria in ripening of fermented products [5]. Both PEDIOCOCCI and homofermentative LACTOBACILLI, as nonstarter lactic acid bacteria, were found to be involved in cheese ripening [6].

The in vitro bioaccessibility of the soluble protein and Maillard reaction products (MRPs) such as furosine (an early indicator of the MR), free FIC (fluorescent intermediate compounds), and FAST index (fluorescence of advanced MRPs and tryptophan), and the level of melanoidins defined by the browning index were analyzed in biscuits formulated from raw and roasted common buckwheat flours fermented by select lactic acid bacteria (LAB). The content of soluble proteins in fermented buckwheat flour and biscuits before and after digestion in vitro was significantly dependent on the LAB applied and the type of flour used and was the highest in the digested biscuits, indicating increased bioaccessibility. Generally, in all analyzed biscuits a lower furosine content was observed as compared to control samples, and its high bioaccessibility was noted after digestion. The free FIC in biscuits was strain-dependent, resulting in low bioaccessibility with the exception of biscuits obtained from both types of flours fermented by Streptococcus thermophilus MK-10. Compared to control biscuits obtained from raw buckwheat flour, the almost twice-increased FAST index was found for samples fermented by L. plantarum IB or Streptococcus thermophilus MK-10. After digestion, at least a fivefold higher value of the browning index was noted in control and tested biscuits, indicating the high bioaccessibility of melanoidins. This study indicates that fermentation of buckwheat flours by selected lactic acid bacteria seems to be a good way to obtain a product with high bioaccessibility of MRPs. However, further research on their functional properties is needed.

Could Modifications of Processing Parameters Enhance the Growth and Selection of Lactic Acid Bacteria in Cold-Smoked Salmon To Improve Preservation by Natural Means?

The aim of the present study was to assess the technological and safety potential of 207 lactic acid bacteria (LAB) and 195 yeast strains isolated from spontaneously fermented Greek wheat sourdoughs. More accurately, the amylolytic, proteolytic, lipolytic, phytase and amino acid decarboxylase activities, along with the production of exopolysaccharides and antimicrobial compounds by the LAB and yeast isolates, were assessed. A well diffusion assay revealed seven proteolytic LAB and eight yeast strains; hydrolysis of tributyrin was evident only in 11 LAB strains. A further Sodium Dodecyl Sulphate-Polyacrylamide Gel Electrophoresis (SDS-PAGE) indicated partial hydrolysis of gluten. Lipolysis kinetics over 21 days was applied, exhibiting that lipolytic activity ranged from 6.25 to 65.50 AU/mL. Thirteen LAB inhibited Penicillium olsonii and Aspergillus niger growth and 12 yeast strains inhibited Pe. chrysogenum growth. Twenty-one Lactiplantibacillus plantarum strains exhibited inhibitory activity against Listeria monocytogenes, as well as several sourdough-associated isolates. The structural gene encoding plantaricin 423 was detected in 19 Lcb. plantarum strains, while the structural genes encoding plantaricins NC8, PlnE/F, PlnJ/K, and S were detected in two Lcb. plantarum strains. None of the microbial strains tested exhibited exopolysaccharide (EPS) production, amino acid decarboxylase, amylolytic or phytase activity. The technological and safety potential of the Lcb. plantarum and Wickerhamomyces anomalus strains was highlighted, since some of them exhibited proteolytic, lipolytic, antibacterial and antimould activities.

Potential for Use of Bacteriocin-Producing Lactic Acid Bacteria in the Preservation of Meats

The process of preliminary isolation and selection of lactic acid bacteria from Vietnamese traditional fermented vegetables is done on the basis of (i) isolation and (ii) qualitative and quantitative analysis of lactic acid as the basis for the inspection and selection of lactic acid bacteria with strong antibacterial characteristics. The selected lactic acid bacteria were applied for yoghurt fermentation with different bacterial densities (104-108 CFU/ml). The changes in pH value during fermentation time and sensory quality of product were evaluated. The research results showed that 48 strains were isolated from Vietnamese traditional fermented vegetables. Among them, 35 isolates (33 rod-shaped and 2 spherical-shaped) met the criteria of lactic acid bacteria. There were 15 isolates that were able to produce the highest amount of lactic acid, in which the rod-shaped bacteria has higher lactic acid production than that of the spherical-shaped. Four strains (S 1.2, S 5.5, S 5.7, XK 1.4) of these 15 strains that were tested antimicrobial activity based on the agar spot test and agar well diffusion test, could produce bacteriocin against Bacillus subtilis. Based on the result of DNA sequencing method, strains XK 1.4 and S 1.2 with strong antibacterial production belonged to Lactobacillus plantarum (similarities 97% and 99%). The yoghurt that was prepared by inoculating 108 cfu/mL of starter cultures (strains XK 1.4 and S 1.2) had the pH value of 4.5 after incubating for 7 hrs, and achieved the good sensory quality.

Lafun is one of the fermented cassava products of West Africa. However, current production systems, which use spontaneous fermentation, result in variable product quality and reduced safety. Therefore, there is an interest in developing a manufacturing process to overcome these challenges. An important element that could resolve the above issues is the use of starter cultures. Therefore, this thesis focuses on the selection of lactic acid bacteria (LAB) from fermenting cassava that have potential use as starter cultures for lafun production and explores their impact on final product quality and safety. Lactic acid bacteria isolates (n=41) from spontaneous fermentation of cassava were characterised and screened for flavour compounds production. Four strains were identified as having the greatest potential use as starter cultures (n=4) and were genotypically identified as Weissella koreensis (2 strains), Lactococcus lactis and Leuconostoc mesenteroides. These four strains were further screened for antibiotic resistant genes and did not seem to contain any such genes. Following starter culture addition, subsequent processing operations may impact on lafun flavour. Therefore, fermentation time and drying of lafun were investigated to enhance the laboratory production of lafun. Acidification rate of the selected isolates was also assessed to also identify possible starter culture combinations where one strain is a strong acidifier while the other enhances flavour. The impact of the developed starters, singly and in combination, on lafun nutritional quality, rheological properties, volatile flavour profile, NMR metabolite profile, cyanide reduction and microbial load was evaluated. Three cassava varieties (Bitter: IBA30527; Fortified: IBA011371; and Sweet: TMEB117) were fermented, in duplicate, to produce samples for analyses. Fermentation for 48 h without pressing the fermented cassava roots favoured the yield of desirable flavour compounds. The results support the adoption of fortified cassava for lafun production due to its positive flavour, nutritional and physical properties.

Lactic acid bacteria (LAB) are an important source of bioactive metabolites and enzymes. LAB isolates from fresh vegetable sources were evaluated to determine their antimicrobial, enzymatic, and adhesion activities. A saline solution from the rinse of each sample was inoculated in De Man, Rogosa and Sharpe Agar (MRS Agar) for isolates recovery. Antimicrobial activity of cell-free supernatants from presumptive LAB isolates was evaluated by microtitration against Gram-positive, Gram-negative, LAB, mold, and yeast strains. Protease, lipase, amylase, citrate metabolism and adhesion activities were also evaluated. Data were grouped using cluster analysis, with 85% of similarity. A total of 76 LAB isolates were recovered, and 13 clusters were formed based on growth inhibition of the tested microorganisms. One cluster had antimicrobial activity against Gram-positive bacteria, molds and yeasts. Several LAB strains, PIM4, ELO8, PIM5 and CAL14 strongly inhibited the growth of L. monocytogenes and JAV15 and TOV9 strongly inhibited the growth of F. oxysporum. Based on enzymatic activities, 5 clusters were formed. Seven isolates hydrolyzed starch, 46 proteins, 14 lipids, and 36 metabolized citrate. LAB isolates with the best activities were molecularly identified as Leuconostoc mesenteroides, Enterococcus mundtii and Enterococcus faecium. Overall, LAB isolated from vegetables showed potential technological applications and should be further evaluated.